A key question for visual neuroscientists is how the brain processes sensory information, especially conflicting or ambiguous stimulation.

One extreme case of ambiguous sensory information is binocular rivalry, where the left eye is given different information to the right eye.

Professor Colin Clifford from the University of Sydney and colleagues set up a binocular rivalry experiment to investigate how the brain processes this visual information.

Five people were presented with different images in their left and right eye. One eye was shown a green windmill rotating clockwise, while the other eye was shown a red windmill rotating anti-clockwise. The participants then reported what they perceived.

The results suggested the brain was processing the conflicting colour information differently to the conflicting motion information.

The brain made sense of the different coloured windmills by blending them together into red and green windmills.

But, when it came to the opposite motions of the windmills, there was no such "binding".

Instead, participants saw either clockwise movement or anti-clockwise movement, with their perception flicking randomly between the two.

Clifford says the findings buy into a long-standing debate in visual neuroscience about how the brain processes different visual inputs such as motion and colour.

Some scientists believe the brain compartmentalises processing of such inputs, whereas others believe processing is integrated across the whole brain, he says.

"The ambiguity in motion is resolved in one way and the ambiguity in colour is resolved in a different way," says Clifford.

If this is the case, he says, the next question is how the brain puts this information back together again to give us a final perception.

Probing consciousness

Clifford says the windmill experiment could also be used to probe the parts of the brain involved in conscious perception.

"Where consciousness is, for want of a better way of putting of it," says Clifford.

The tests would be run again while scanning the participants' brains to check what parts were active at different stages.

The brain activity would be monitored as the participants reported what colours and motion they were seeing.

"If we can find parts of the brain whose activity fluctuates in sync with the perceptual changes, then we have evidence that part of the brain underlies the conscious experience of the person," says Clifford.